Banpod Konkam, 45, said his teenage son had only intended to visit the cave for an hour before getting stranded.

Describing the night that Dom, 13, disappeared, he explained: When I arrived [at the cave] a rescue team was trying to go in. The flood came up to their waists, so they came out and waited. When they tried again the water was up to their chests, that’s when they realised it was impossible to go in and help the boys.

Dom is the captain of the Wild Boars football team and had his 13th birthday in the cave.

His family said he lost about half a stone (four kilograms) during his ordeal, but that his health is improving.

His grandmother, Kamauey Phromthep, 64, said he told relatives from his hospital bed that the weather had changed so quickly that they could not escape.

When he went in, everything was pretty normal: the sky was as bright as it can be and there was no rain or flooding, she told Sky News.

It was actually a really beautiful day. While they were inside, the flash flood started to fill the cave. The boys then ran to dryer and higher ground. Dom said wherever he could find holes, they would dig through it so that they could be safe.

The family said they had started to fear the worst when British divers finally found the team.

Mr Konkam added: I was so speechless and overwhelmed by that news. They are true heroes to my family.

However, their initial joy at them being discovered alive soon turned to fear when they discovered the boys would have to dive to safety.

Mrs Phromthep said: I was so worried about him. He’d had nothing to eat for 10 days, he was still weak and I was afraid that mission would fail.

The dramatic rescue mission involved 13 foreign divers – around half of which were British – and the youngsters were given a minor tranquilliser to calm their nerves, according to Thailand’s junta chief.

The boys had gone missing while exploring the cave after football practice with their coach on 23 June, but bursts of monsoon rain caused the water inside the cave to rise, leaving them trapped.

The boys’ football team – the Wild Boars – has returned to training for the first time since the rescue operation.

The session at a school in the Mae Sai district of Chiang Rai province was led by head coach Nopparat Khantavong, and the youngsters involved said they could not wait to see their friends back on the pitch.